Single photon emission computed tomography (SPECT) has become an important diagnostic tool in nuclear medicine clinics today. In particular, cardiovascular SPECT imaging has become the predominant application of all clinical SPECT procedures. Most SPECT procedures are accomplished using a large field-of-view rotating gamma camera with parellel collimator. If converging collimators were used instead of parallel collimators, these same cameras could offer a significant increase in sensitivity. Converging collimators have not previously been used on SPECT systems for imaging the heart because of algorithm complexity, truncation of projection data, and additional attenuation due to angular sampling requirements of greater than 180 degrees. Imaging with convergent hole collimators using present large field of view rotating gamma cameras has significant potential for improved spatial and contrast resolution of cardiac imaging. This is important for better detection of myocardial infarction and diagnosis of ischemic heart disease. The goal of this proposal is to provide a systematic quantitative evaluation of three types of geometries in terms of image quality and measurement accuracy. The importance of the proposed research is to provide the scientific basis for establishing guidelines for the selection and specification of collimators and algorithms. The intent of this work is to improve patient care without any cost increase in present cardiac SPECT procedures. The aim of this proposal is to design optimum collimators for both fan beam and cone beam geometries and to develop algorithms that reconstruct transaxial images from projections without artifacts. In particular, comparisons will be made between parallel geometry, fan beam geometry, and cone beam geometry for advantages and disadvantages in terms of image quality, quantitation, lesion detectability, and sizing of lesions.